public class Main {
    public static void main(String[] args) {
        //Fractional series summation
        //计算1/1-1/2+1/3-1/4+1/5 …… + 1/99 - 1/100 的值    。
        double sum = 0;
        for (int i = 1; i <= 100; i++){
            int flag = 1;
            if(i % 2 == 0){
                flag = -flag;
            }
            sum += flag * (1.0 / i);
        }
        System.out.println(sum);
    }
}